Polyphenylene ether/polystyrene (PPE/PS) blends are attractive for uses requiring strength. However, unmodified PPE/PS blends have poor impact resistance. The most promising impact modifier for PPE/PS blends has been a high molecular weight styrenic block copolymer. However, the high molecular weight of the copolymer modifier leads to PPE/PS blends with reduced melt flow and, thus, reduced processability. Therefore, a modifier which can improve impact resistance of PPE/PS blends and which maintains good melt flow would be highly desirable.